Mixed solvothermal synthesis of hierarchical ZnIn sub(2)S sub(4) spheres: specific facet-induced photocatalytic activity enhancement and a DFT elucidation

A series of ZnIn sub(2)S sub(4) materials have been synthesized by a simple mixed solvothermal process in a water-ethanol solution. It was found that the solvent composition had a large impact on the photocatalytic activity. A fluffy structure of ZnIn sub(2)S sub(4) synthesized with 1.5 mL of water presents the highest H sub(2) evolution rate (268 mu mol h super(-1)) under visible light ( lambda > 400 nm) in a SO sub(3) super(2-)/S super(2-) aqueous solution. Combining results from TEM, the intensity ratio of diffraction peaks and dye adsorption analysis, we found that the increase of {100} facets generated in the mixed solvothermal process led to a distinct enhancement of photoreactivity. To investigate the origin of the facet-dependent photocatalytic activity, an electrostatic potential calculation was conducted to investigate the electron process, which indicated that photoexcited carriers preferentially migrate to atomic steps on the {100} facets. This cooperative effect between the {100} facets and the electron diffusion process meant that the {100} facets improve the photoreactivity of ZnIn sub(2)S sub(4).